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Lee S, Seo YE, Choi J, Yan X, Kim T, Choi D, Lee JH. Nucleolar actions in plant development and stress responses. PLANT, CELL & ENVIRONMENT 2024. [PMID: 39169813 DOI: 10.1111/pce.15099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2024] [Revised: 08/09/2024] [Accepted: 08/10/2024] [Indexed: 08/23/2024]
Abstract
The nucleolus is conventionally acknowledged for its role in ribosomal RNA (rRNA) synthesis and ribosome biogenesis. Recent research has revealed its multifaceted involvement in plant biology, encompassing regulation of the cell cycle, development, and responses to environmental stresses. This comprehensive review explores the diverse roles of the nucleolus in plant growth and responses to environmental stresses. The introduction delves into its traditional functions in rRNA synthesis and potential participation in nuclear liquid-liquid phase separation. By examining the multifaceted roles of nucleolar proteins in plant development, we highlight the impacts of various nucleolar mutants on growth, development, and embryogenesis. Additionally, we reviewed the involvement of nucleoli in responses to abiotic and biotic stresses. Under abiotic stress conditions, the nucleolar structure undergoes morphological changes. In the context of biotic stress, the nucleolus emerges as a common target for effectors of pathogens for manipulation of host immunity to enhance pathogenicity. The detailed exploration of how pathogens interact with nucleoli and manipulate host responses provides valuable insights into plant stress responses as well as plant growth and development. Understanding these processes may pave the way for promising strategies to enhance crop resilience and mitigate the impact of biotic and abiotic stresses in agricultural systems.
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Affiliation(s)
- Soeui Lee
- Plant Immunity Research Center, Seoul National University, Seoul, South Korea
- Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, South Korea
| | - Ye-Eun Seo
- Plant Immunity Research Center, Seoul National University, Seoul, South Korea
- Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, South Korea
- Department of Agriculture, Forestry and Bioresources, College of Agriculture and Life Science, Plant Genomics and Breeding Institute, Seoul National University, Seoul, South Korea
| | - Jeen Choi
- Plant Immunity Research Center, Seoul National University, Seoul, South Korea
- Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, South Korea
- Department of Agriculture, Forestry and Bioresources, College of Agriculture and Life Science, Plant Genomics and Breeding Institute, Seoul National University, Seoul, South Korea
| | - Xin Yan
- Plant Immunity Research Center, Seoul National University, Seoul, South Korea
- Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, South Korea
- Department of Agriculture, Forestry and Bioresources, College of Agriculture and Life Science, Plant Genomics and Breeding Institute, Seoul National University, Seoul, South Korea
| | - Taewon Kim
- Plant Immunity Research Center, Seoul National University, Seoul, South Korea
- Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, South Korea
- Department of Agriculture, Forestry and Bioresources, College of Agriculture and Life Science, Plant Genomics and Breeding Institute, Seoul National University, Seoul, South Korea
| | - Doil Choi
- Plant Immunity Research Center, Seoul National University, Seoul, South Korea
- Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, South Korea
- Department of Agriculture, Forestry and Bioresources, College of Agriculture and Life Science, Plant Genomics and Breeding Institute, Seoul National University, Seoul, South Korea
| | - Joo Hyun Lee
- Plant Immunity Research Center, Seoul National University, Seoul, South Korea
- Research Institute of Agriculture and Life Sciences, Seoul National University, Seoul, South Korea
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Kutashev KO, Franek M, Diamanti K, Komorowski J, Olšinová M, Dvořáčková M. Nucleolar rDNA folds into condensed foci with a specific combination of epigenetic marks. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2021; 105:1534-1548. [PMID: 33314374 DOI: 10.1111/tpj.15130] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2020] [Accepted: 11/30/2020] [Indexed: 05/15/2023]
Abstract
Arabidopsis thaliana 45S ribosomal genes (rDNA) are located in tandem arrays called nucleolus organizing regions on the termini of chromosomes 2 and 4 (NOR2 and NOR4) and encode rRNA, a crucial structural element of the ribosome. The current model of rDNA organization suggests that inactive rRNA genes accumulate in the condensed chromocenters in the nucleus and at the nucleolar periphery, while the nucleolus delineates active genes. We challenge the perspective that all intranucleolar rDNA is active by showing that a subset of nucleolar rDNA assembles into condensed foci marked by H3.1 and H3.3 histones that also contain the repressive H3K9me2 histone mark. By using plant lines containing a low number of rDNA copies, we further found that the condensed foci relate to the folding of rDNA, which appears to be a common mechanism of rDNA regulation inside the nucleolus. The H3K9me2 histone mark found in condensed foci represents a typical modification of bulk inactive rDNA, as we show by genome-wide approaches, similar to the H2A.W histone variant. The euchromatin histone marks H3K27me3 and H3K4me3, in contrast, do not colocalize with nucleolar foci and their overall levels in the nucleolus are very low. We further demonstrate that the rDNA promoter is an important regulatory region of the rDNA, where the distribution of histone variants and histone modifications are modulated in response to rDNA activity.
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Affiliation(s)
- Konstantin O Kutashev
- Mendel Centre for Plant Genomics and Proteomics, CEITEC, Masaryk University, Kamenice 5, Brno, 62500, Czech Republic
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Kotlářská 2, Brno, 61137, Czech Republic
| | - Michal Franek
- Mendel Centre for Plant Genomics and Proteomics, CEITEC, Masaryk University, Kamenice 5, Brno, 62500, Czech Republic
| | - Klev Diamanti
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, 751 24, Sweden
- Department of Immunology, Genetics and Pathology, Uppsala University, Uppsala, 751 08, Sweden
| | - Jan Komorowski
- Department of Cell and Molecular Biology, Uppsala University, Uppsala, 751 24, Sweden
- Institute of Computer Science, Polish Academy of Sciences, Warsaw, 012-48, Poland
| | - Marie Olšinová
- BioCEV Imaging Methods Core Facility, Průmyslová 595, Vestec, 252 50, Czech Republic
| | - Martina Dvořáčková
- Mendel Centre for Plant Genomics and Proteomics, CEITEC, Masaryk University, Kamenice 5, Brno, 62500, Czech Republic
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Manzano A, Villacampa A, Sáez-Vásquez J, Kiss JZ, Medina FJ, Herranz R. The Importance of Earth Reference Controls in Spaceflight -Omics Research: Characterization of Nucleolin Mutants from the Seedling Growth Experiments. iScience 2020; 23:101686. [PMID: 33163940 PMCID: PMC7607443 DOI: 10.1016/j.isci.2020.101686] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2020] [Revised: 09/04/2020] [Accepted: 10/10/2020] [Indexed: 01/23/2023] Open
Abstract
Understanding plant adaptive responses to the space environment is a requisite for enabling space farming. Spaceflight produces deleterious effects on plant cells, particularly affecting ribosome biogenesis, a complex stress-sensitive process coordinated with cell division and differentiation, known to be activated by red light. Here, in a series of ground studies, we have used mutants from the two Arabidopsis nucleolin genes (NUC1 and NUC2, nucleolar regulators of ribosome biogenesis) to better understand their role in adaptive response mechanisms to stress on Earth. Thus, we show that nucleolin stress-related gene NUC2 can compensate for the environmental stress provided by darkness in nuc1 plants, whereas nuc2 plants are not able to provide a complete response to red light. These ground control findings, as part of the ESA/NASA Seedling Growth spaceflight experiments, will determine the basis for the identification of genetic backgrounds enabling an adaptive advantage for plants in future space experiments.
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Affiliation(s)
- Aránzazu Manzano
- Centro de Investigaciones Biológicas Margarita Salas (CSIC), Ramiro de Maeztu 9, 28040, Madrid, Spain
| | - Alicia Villacampa
- Centro de Investigaciones Biológicas Margarita Salas (CSIC), Ramiro de Maeztu 9, 28040, Madrid, Spain
| | - Julio Sáez-Vásquez
- CNRS, Laboratoire Génome et Développement des Plantes (LGDP), UMR 5096, 66860 Perpignan, France
- Univ. Perpignan Via Domitia, LGDP, UMR 5096, 66860 Perpignan, France
| | - John Z. Kiss
- Department of Biology, University of North Carolina-Greensboro, Greensboro, NC 27402, USA
| | - F. Javier Medina
- Centro de Investigaciones Biológicas Margarita Salas (CSIC), Ramiro de Maeztu 9, 28040, Madrid, Spain
| | - Raúl Herranz
- Centro de Investigaciones Biológicas Margarita Salas (CSIC), Ramiro de Maeztu 9, 28040, Madrid, Spain
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Shubina MY, Arifulin EA, Sorokin DV, Sosina MA, Tikhomirova MA, Serebryakova MV, Smirnova T, Sokolov SS, Musinova YR, Sheval EV. The GAR domain integrates functions that are necessary for the proper localization of fibrillarin (FBL) inside eukaryotic cells. PeerJ 2020; 8:e9029. [PMID: 32377452 PMCID: PMC7194090 DOI: 10.7717/peerj.9029] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 03/31/2020] [Indexed: 01/25/2023] Open
Abstract
Fibrillarin (FBL) is an essential nucleolar protein that participates in pre-rRNA methylation and processing. The methyltransferase domain of FBL is an example of an extremely well-conserved protein domain in which the amino acid sequence was not substantially modified during the evolution from Archaea to Eukaryota. An additional N-terminal glycine–arginine-rich (GAR) domain is present in the FBL of eukaryotes. Here, we demonstrate that the GAR domain is involved in FBL functioning and integrates the functions of the nuclear localization signal and the nucleolar localization signal (NoLS). The methylation of the arginine residues in the GAR domain is necessary for nuclear import but decreases the efficiency of nucleolar retention via the NoLS. The presented data indicate that the GAR domain can be considered an evolutionary innovation that integrates several functional activities and thereby adapts FBL to the highly compartmentalized content of the eukaryotic cell.
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Affiliation(s)
- Maria Y Shubina
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Eugene A Arifulin
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Dmitry V Sorokin
- Laboratory of Mathematical Methods of Image Processing, Faculty of Computational Mathematics and Cybernetics, Lomonosov Moscow State University, Moscow, Russia
| | - Mariya A Sosina
- Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia
| | - Maria A Tikhomirova
- Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia.,Faculty of Bioengineering and Bioinformatics, Lomonosov Moscow State University, Moscow, Russia
| | - Marina V Serebryakova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Tatiana Smirnova
- Department of Cell Biology and Histology, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Svyatoslav S Sokolov
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia
| | - Yana R Musinova
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.,Koltzov Institute of Developmental Biology, Russian Academy of Sciences, Moscow, Russia.,Skobelkin State Scientific Center of Laser Medicine FMBA, Moscow, Russia
| | - Eugene V Sheval
- Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State University, Moscow, Russia.,Department of Cell Biology and Histology, Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia.,LIA 1066 LFR2O French-Russian Joint Cancer Research Laboratory, Villejuif, France
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5
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Dvořáčková M, Fajkus J. Visualization of the Nucleolus Using Ethynyl Uridine. FRONTIERS IN PLANT SCIENCE 2018; 9:177. [PMID: 29503656 PMCID: PMC5820300 DOI: 10.3389/fpls.2018.00177] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 01/30/2018] [Indexed: 05/04/2023]
Abstract
Thanks to recent innovative methodologies, key cellular processes such as replication or transcription can be visualized directly in situ in intact tissues. Many studies use so-called click iT chemistry where nascent DNA can be tracked by 5-ethynyl-2'-deoxyuridine (EdU), and nascent RNA by 5-ethynyl uridine (EU). While the labeling of replicating DNA by EdU has already been well established and further exploited in plants, the use of EU to reveal nascent RNA has not been developed to such an extent. In this article, we present a protocol for labeling of nucleolar RNA transcripts using EU and show that EU effectively highlights the nucleolus. The method is advantageous, because the need to prepare transgenic plants expressing fluorescently tagged nucleolar components when the nucleolus has to be visualized can be avoided.
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Affiliation(s)
- Martina Dvořáčková
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Brno, Czechia
- *Correspondence: Martina Dvořáčková, Jiří Fajkus, ;
| | - Jiří Fajkus
- Mendel Centre for Plant Genomics and Proteomics, Central European Institute of Technology, Masaryk University, Brno, Czechia
- Laboratory of Functional Genomics and Proteomics, National Centre for Biomolecular Research, Faculty of Science, Masaryk University, Brno, Czechia
- Institute of Biophysics, Academy of Sciences of the Czech Republic, Brno, Czechia
- *Correspondence: Martina Dvořáčková, Jiří Fajkus, ;
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Kalinina NO, Makarova S, Makhotenko A, Love AJ, Taliansky M. The Multiple Functions of the Nucleolus in Plant Development, Disease and Stress Responses. FRONTIERS IN PLANT SCIENCE 2018; 9:132. [PMID: 29479362 PMCID: PMC5811523 DOI: 10.3389/fpls.2018.00132] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2017] [Accepted: 01/23/2018] [Indexed: 05/18/2023]
Abstract
The nucleolus is the most conspicuous domain in the eukaryotic cell nucleus, whose main function is ribosomal RNA (rRNA) synthesis and ribosome biogenesis. However, there is growing evidence that the nucleolus is also implicated in many other aspects of cell biology, such as regulation of cell cycle, growth and development, senescence, telomerase activity, gene silencing, responses to biotic and abiotic stresses. In the first part of the review, we briefly assess the traditional roles of the plant nucleolus in rRNA synthesis and ribosome biogenesis as well as possible functions in other RNA regulatory pathways such as splicing, nonsense-mediated mRNA decay and RNA silencing. In the second part of the review we summarize recent progress and discuss already known and new hypothetical roles of the nucleolus in plant growth and development. In addition, this part will highlight studies showing new nucleolar functions involved in responses to pathogen attack and abiotic stress. Cross-talk between the nucleolus and Cajal bodies is also discussed in the context of their association with poly(ADP ribose)polymerase (PARP), which is known to play a crucial role in various physiological processes including growth, development and responses to biotic and abiotic stresses.
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Affiliation(s)
- Natalia O. Kalinina
- Branch of the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow, Russia
- Natalia O. Kalinina
| | - Svetlana Makarova
- Branch of the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow, Russia
| | - Antonida Makhotenko
- Branch of the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow, Russia
| | | | - Michael Taliansky
- Branch of the Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry of the Russian Academy of Sciences, Moscow, Russia
- The James Hutton Institute, Dundee, United Kingdom
- *Correspondence: Michael Taliansky
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7
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Shubina MY, Musinova YR, Sheval EV. Nucleolar methyltransferase fibrillarin: Evolution of structure and functions. BIOCHEMISTRY (MOSCOW) 2016; 81:941-50. [DOI: 10.1134/s0006297916090030] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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8
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Durut N, Sáez-Vásquez J. Nucleolin: dual roles in rDNA chromatin transcription. Gene 2015; 556:7-12. [PMID: 25225127 DOI: 10.1016/j.gene.2014.09.023] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Revised: 09/08/2014] [Accepted: 09/09/2014] [Indexed: 01/17/2023]
Abstract
Nucleolin is a major nucleolar protein conserved in all eukaryotic organisms. It is a multifunctional protein involved in different cellular aspects like chromatin organization and stability, DNA and RNA metabolism, assembly of ribonucleoprotein complexes, cytokinesis, cell proliferation and stress response. The multifunctionality of nucleolin is linked to its tripartite structure, post-translational modifications and its ability of shuttling from and to the nucleolus/nucleoplasm and cytoplasm. Nucleolin has been now studied for many years and its activities and properties have been described in a number of excellent reviews. Here, we overview the role of nucleolin in RNA polymerase I (RNAPI) transcription and describe recent results concerning its functional interaction with rDNA chromatin organization. For a long time, nucleolin has been associated with rRNA gene expression and pre-rRNA processing. However, the functional connection between nucleolin and active versus inactive rRNA genes is still not fully understood. Novel evidence indicates that the nucleolin protein might be required for controlling the transcriptional ON/OFF states of rDNA chromatin in both mammals and plants.
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Affiliation(s)
- Nathalie Durut
- CNRS, Laboratoire Génome et Développement des Plantes, UMR 5096, 66860 Perpignan, France; Univ. Perpignan Via Domitia, Laboratoire Génome et Développement des Plantes, UMR 5096, F-66860 Perpignan, France
| | - Julio Sáez-Vásquez
- CNRS, Laboratoire Génome et Développement des Plantes, UMR 5096, 66860 Perpignan, France; Univ. Perpignan Via Domitia, Laboratoire Génome et Développement des Plantes, UMR 5096, F-66860 Perpignan, France.
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A charge-dependent mechanism is responsible for the dynamic accumulation of proteins inside nucleoli. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:101-10. [DOI: 10.1016/j.bbamcr.2014.10.007] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 10/02/2014] [Accepted: 10/06/2014] [Indexed: 01/19/2023]
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10
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Stępiński D. Functional ultrastructure of the plant nucleolus. PROTOPLASMA 2014; 251:1285-306. [PMID: 24756369 PMCID: PMC4209244 DOI: 10.1007/s00709-014-0648-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 04/08/2014] [Indexed: 05/23/2023]
Abstract
Nucleoli are nuclear domains present in almost all eukaryotic cells. They not only specialize in the production of ribosomal subunits but also play roles in many fundamental cellular activities. Concerning ribosome biosynthesis, particular stages of this process, i.e., ribosomal DNA transcription, primary RNA transcript processing, and ribosome assembly proceed in precisely defined nucleolar subdomains. Although eukaryotic nucleoli are conservative in respect of their main function, clear morphological differences between these structures can be noticed between individual kingdoms. In most cases, a plant nucleolus shows well-ordered structure in which four main ultrastructural components can be distinguished: fibrillar centers, dense fibrillar component, granular component, and nucleolar vacuoles. Nucleolar chromatin is an additional crucial structural component of this organelle. Nucleolonema, although it is not always an unequivocally distinguished nucleolar domain, has often been described as a well-grounded morphological element, especially of plant nucleoli. The ratios and morphology of particular subcompartments of a nucleolus can change depending on its metabolic activity which in turn is correlated with the physiological state of a cell, cell type, cell cycle phase, as well as with environmental influence. Precise attribution of functions to particular nucleolar subregions in the process of ribosome biosynthesis is now possible using various approaches. The presented description of plant nucleolar morphology summarizes previous knowledge regarding the function of nucleoli as well as of their particular subdomains not only in the course of ribosome biosynthesis.
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Affiliation(s)
- Dariusz Stępiński
- Department of Cytophysiology, Faculty of Biology and Environmental Protection, University of Łódź, Pomorska 141/143, 90-236, Łódź, Poland,
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11
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Nucleolin, a major conserved multifunctional nucleolar phosphoprotein of proliferating cells. J Appl Biomed 2010. [DOI: 10.2478/v10136-009-0017-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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12
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Stepiński D. Organization of the nucleoli of soybean root meristematic cells at different states of their activity. Micron 2010; 41:283-8. [PMID: 20071186 DOI: 10.1016/j.micron.2009.11.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2009] [Revised: 11/23/2009] [Accepted: 11/25/2009] [Indexed: 10/20/2022]
Abstract
Internal organization of a nucleolus changes along with rRNA transcriptional activity. These changes mainly concern qualitative and quantitative alternations of three main nucleolar components: fibrillar centres (FC), dense fibrillar component (DFC) and granular component (GC). In the present work quantitative measurements of the number and sizes of FCs and DFCs in nucleoli of root meristematic cells of soybean seedlings grown at (1) chilling conditions that reduce transcriptional activity of soybean nucleoli (temp. of 10 degrees C) and at (2) conditions that increase this activity (recovery at optimal temp. of 25 degrees C after previous chilling), even more than (3) the control, have been carried out. Morphometric measurements showed that the highest number of FCs and DFCs was in the most active nucleoli, while the smallest number - in those with the lowest activity. The average size of an individual FC was similar in all nucleoli regardless of their transcriptional activity, that of the individual DFC varied, being bigger in the nucleoli of the chilled plants and smallest in those of the recovered plants. The numbers of FCs and DFCs seem to be indicators of transcriptional activity of plant nucleoli - the higher number of FCs and DFCs the more active nucleoli.
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Affiliation(s)
- Dariusz Stepiński
- Department of Cytophysiology, University of Łódź, Pilarskiego 14, 90-321 Łódź, Poland.
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Stepiński D. Immunodetection of nucleolar proteins and ultrastructure of nucleoli of soybean root meristematic cells treated with chilling stress and after recovery. PROTOPLASMA 2009; 235:77-89. [PMID: 19241118 DOI: 10.1007/s00709-009-0033-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2008] [Accepted: 01/19/2009] [Indexed: 05/03/2023]
Abstract
The nucleolar proteins, fibrillarin and nucleophosmin, have been identified immunofluorescently in the root meristematic cells of soybean seedlings under varying experimental conditions: at 25 degrees C (control), chilling at 10 degrees C for 3 h and 4 days and recovery from the chilling stress at 25 degrees C. In each experimental variant, the immunofluorescence signals were present solely at the nucleolar territories. Fluorescent staining for both proteins was mainly in the shape of circular domains that are assumed to correspond to the dense fibrillar component of the nucleoli. The fewest fluorescent domains were observed in the nucleoli of chilled plants, and the highest number was observed in the plants recovered after chilling. This difference in the number of circular domains in the nucleoli of each variant may indicate various levels of these proteins in each variant. Both the number of circular domains and the level of these nucleolar proteins changed with changes in the transcriptional activity of the nucleoli, with the more metabolically active cell having higher numbers of active areas in the nucleolus and higher levels of nucleolar proteins, and conversely. Electron microscopic studies revealed differences in the ultrastructure of the nucleoli in all experimental variants and confirmed that the number of fibrillar centres surrounded by dense fibrillar component was the lowest in the nucleoli of chilled plants, and the highest in the nucleoli of recovered seedlings.
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Affiliation(s)
- Dariusz Stepiński
- Department of Cytophysiology, University of Łódź, Pilarskiego 14, 90-231, Łódź, Poland.
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Long H, He J, Sun H, Hao S, Jiao M. In situ comparative studies on subnucleolar distribution and configuration of plant rDNA. Micron 2008; 39:405-10. [PMID: 18262427 DOI: 10.1016/j.micron.2007.03.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2006] [Revised: 03/01/2007] [Accepted: 03/02/2007] [Indexed: 11/30/2022]
Abstract
The distribution and configurations of nucleolar DNA in Pisum sativum L., Allium sativum L., Triticum aestivum L. were analyzed by specific cytochemical staining using NAMA-Ur. It has been observed that in the nucleoli of different plant species, the DNA occupied different positions in different areas, which may imply a different status and strategy of rDNA transcription. Our results showed irregular clumps of rDNA surrounding FCs in semi-circular formations in P. sativum and T. aestivum, indicating a regular pattern of rDNA distribution and supporting the helix model of rDNA configuration. The rDNA was condensed in some regions and uncondensed in others. Nucleolus-associated chromatin extended from outside the nucleolus to the periphery of the FCs via nucleolar channels, which suggests a possible origin for nucleolar DNA.
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Affiliation(s)
- Hong Long
- College of Life Science and Technology, Huazhong Agricultural University, Wuhan 430070, PR China
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Sobol MA, González-Camacho F, Kordyum EL, Medina FJ. Nucleolar proteins change in altered gravity. J Appl Biomed 2007. [DOI: 10.32725/jab.2007.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
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17
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Sobol M, Gonzalez-Camacho F, Rodríguez-Vilariño V, Kordyum E, Medina FJ. Subnucleolar location of fibrillarin and NopA64 in Lepidium sativum root meristematic cells is changed in altered gravity. PROTOPLASMA 2006; 228:209-19. [PMID: 16838080 DOI: 10.1007/s00709-006-0157-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2005] [Accepted: 10/11/2005] [Indexed: 05/10/2023]
Abstract
Fibrillarin and the plant nucleolin homolog NopA64 are two important nucleolar proteins involved in pre-rRNA processing. In order to determine the effects of the altered gravity environment on the nucleolus, we have investigated the location of fibrillarin and NopA64 in nucleolar subcomponents of cress (Lepidium sativum L.) root meristematic cells grown under clinorotation, which reproduces an important feature of microgravity, namely, the absence of the orienting action of a gravity vector, and compared it to the location in control cells grown in normal 1 g conditions. Prior to these experiments, we report here the characterization of cress fibrillarin as a 41 kDa protein which can be isolated from meristematic cells in three nuclear fractions, namely, the soluble ribonucleoprotein fraction, the chromatin fraction, and the nuclear-matrix fraction. Furthermore, as reported for other species, the location of both fibrillarin and NopA64 in the cress cell nucleolus was in zones known to contain complex ribonucleoprotein particles involved in early pre-rRNA processing, i.e., processomes. Under altered gravity, a decrease in the quantity of both fibrillarin and NopA64 compared to controls was observed in the transition zone between fibrillar centers and the dense fibrillar component, as well as in the bulk of the dense fibrillar component. These data suggest that altered (reduced) gravity results in a lowered level of functional activity in the nucleolus.
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Affiliation(s)
- M Sobol
- Centro de Investigaciones Biológicas, Consejo Superior de Investigaciones Cientificas, Madrid, Spain
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González-Camacho F, Medina FJ. The nucleolar structure and the activity of NopA100, a nucleolin-like protein, during the cell cycle in proliferating plant cells. Histochem Cell Biol 2006; 125:139-53. [PMID: 16217651 DOI: 10.1007/s00418-005-0081-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/13/2005] [Indexed: 11/27/2022]
Abstract
For the purpose of gaining knowledge of the relationships between cell proliferation and ribosome biogenesis, as two fundamental mutually interconnected cellular processes, studies were performed on cell populations synchronized in their cell-cycle progression by treatment with hydroxyurea, followed by sampling at different times after its removal. A structural rearrangement of the nucleolus was observed throughout the interphase, along with changes in the relative amounts of different nucleolar subcomponents. A structural model of nucleolar organization was associated with each interphase period. Throughout interphase, the nucleolin-like protein, NopA100, was immunodetected in the dense fibrillar component of the nucleolus, preferentially near fibrillar centers and its levels were shown to increase from G1 to G2. A western blotting analysis of soluble nuclear protein extracts with anti-NopA100 antibody resulted in the intense labeling of a 100-kDa band, but also of a series of proteins related to it, suggesting that NopA100 undergoes a physiological process of proteolytic maturation, similar to that described for mammalian nucleolin, but not reported in other biological model systems. Physiological proteolysis of NopA100, related to cell-cycle progression, was confirmed after the nuclei extracted from synchronized cells were treated with the protease inhibitor, leupeptin, which resulted in an increase of the 100-kDa band at the expenses of the decrease of some other bands, according to the cell-cycle stages. We therefore conclude that there is a relationship between the increase in nucleolar activity, cell-cycle progression, nucleolar structure, the activity of NopA100, and the proteolysis of this nucleolin-like protein.
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Sato S, Yano H, Makimoto Y, Kaneta T, Sato Y. Nucleolonema as a fundamental substructure of the nucleolus. JOURNAL OF PLANT RESEARCH 2005; 118:71-81. [PMID: 15843864 DOI: 10.1007/s10265-005-0204-8] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/21/2004] [Accepted: 03/04/2005] [Indexed: 05/03/2023]
Abstract
The nucleolus is the most obvious structure in the eukaryotic nucleus. It is known to be a ribosome-producing apparatus where ribosomal (r) DNA is transcribed and the primary rRNA transcripts are processed to produce three of the four rRNA species. Electron microscopy has shown that the nucleolus consists of three major components, a dense fibrillar component (DFC), a granular component (GC) and a fibrillar center (FC). The DFC and FCs are integrated into a fundamental nucleolar substructure called the nucleolonema. The DFC corresponds to the matrix of the nucleolonema, and the FC is an electron microscopic counterpart of argyrophobic lacunae localized in the nucleolonema. The spherical FCs are intermittently arranged along the length of the nucleolonema in actively growing cells but are fused with each other to form tubular FCs when rDNA transcription is hampered. The RNase-gold complex does not bind to the FC but to the DFC and the GC, suggesting that rDNA transcription does not occur in the FC although both fluorescence in situ hybridization (FISH) and electron microscopic in situ hybridization reveal that the rDNA is specifically localized in the FCs. Immunogold-labeling after bromo-UTP (BrUTP) incorporation shows that rDNA transcription takes place in the boundary region between the FC and the DFC, and primary rRNA transcripts are expected to be processed outward within the DFC. Data have accumulated suggesting that the nucleolonema is a fundamental substructure of the nucleolus, and its skeleton is the tandem arrangement of the FCs, which are resting harbors or storages of rDNA. This paper proposes that the transversal structural organization of the nucleolonema is centrifugally built up by several structural and functional domains: condensed and/or loosened rDNA, rDNA transcription zone, and transcript processing and ribosome assembly zones.
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Affiliation(s)
- Seiichi Sato
- Department of Biology, Faculty of Science, Ehime University, Matsuyama, 790-8577, Japan.
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Hemleben V, Volkov RA, Zentgraf U, Medina FJ. Molecular Cell Biology: Organization and Molecular Evolution of rDNA, Nucleolar Dominance, and Nucleolus Structure. PROGRESS IN BOTANY 2004. [DOI: 10.1007/978-3-642-18819-0_5] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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21
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Iwano M, Che FS, Takayama S, Fukui K, Isogai A. Three-dimensional architecture of ribosomal DNA within barley nucleoli revealed with electron microscopy. SCANNING 2003; 25:257-63. [PMID: 14748389 DOI: 10.1002/sca.4950250507] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/02/2023]
Abstract
To elucidate the topological positioning of ribosomal RNA genes (rDNA) and nucleolar structure in three dimensions, we examined the localization of rDNA using in situ hybridization (ISH) analysis by scanning electron microscopy (SEM). The rDNA genes within the three-dimensional architecture of nucleoli were detected on chromatin fibers that connect a thick strand-like structure and a protrusion of rDNA into the inner nuclear hole where the nucleolus is formed. This novel use of ISH together with SEM is useful for the analysis of nucleolar structure in detail. Furthermore, rDNA was detected at the periphery of the fibrillar centers (FCs) of the nucleolus using immuno-gold labeling together with transmission electron microscopy (TEM). In situ hybridization with TEM confirmed that rDNA is naked and thus active in the FCs of nucleoli; ISH with SEM confirmed that rDNA is not covered with ribonucleo proteins at the protruding point and is thus inactive. We also show that the distribution pattern of FCs differs from sample to sample. These results indicate that rDNA is transcribed dynamically in a time- and region-specific manner over the course of the cell cycle.
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Affiliation(s)
- Megumi Iwano
- Graduate School of Biological Sciences, Nara Institute of Science and Technology, Nara, Japan.
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Chang WL, Lee DC, Leu S, Huang YM, Lu MC, Ouyang P. Molecular characterization of a novel nucleolar protein, pNO40. Biochem Biophys Res Commun 2003; 307:569-77. [PMID: 12893261 DOI: 10.1016/s0006-291x(03)01208-7] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
We report the discovery and characterization of a novel nucleolar protein. This protein, referred to as pNO40 based on its molecular weight on SDS-PAGE, was identified through yeast two hybrid interaction screen of a human kidney cDNA library using pinin (pnn) protein as the bait. The deduced amino acids of pNO40 derived from cDNA cloning of diverse species display high conservation; 95% identify between human and mouse and 57.3% identity for human and zebrafish. Several distinct domains are discernable in the ORF of pNO40, including a ribosomal protein S1 RNA binding region, a CCHC type zinc finger, and clusters of basic amino acid representing potential nucleolar targeting signal. Immunostaining of endogenous or transfected pNO40 indicated that it is localized to nucleoli of diverse cultured cells, with some concentration in the granular component of nucleoli. Northern blot analysis demonstrated that pNO40 message is expressed ubiquitously across all tissues examined. Characterization of human and mouse pNO40 gene revealed that mouse gene spans 44 kb in length and contains 8 exons, while that of human is 68 kb in length and displays two isoforms generated by alternative splicing of the 5(')-untranslated region and differential usage of translation start site. Based on sequence features and its subcellular location, we predict that pNO40 is a novel nucleolar protein with function related to ribosome maturation and/or biogenesis.
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Affiliation(s)
- Wei-Lun Chang
- Department of Anatomy, Chang Gung University Medical College, Taiwan, 33101
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Wei T, Baiqu H, Chunxiang L, Zhonghe Z. In situ visualization of rDNA arrangement and its relationship with subnucleolar structural regions in Allium sativum cell nucleolus. J Cell Sci 2003; 116:1117-25. [PMID: 12584254 DOI: 10.1242/jcs.00323] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We used a DNA-specific staining technique to show the two states of DNA component distributed in the nucleolar region of Allium sativum cells. One state is the extended DNA fiber, and the other is the condensed DNA clump. In situ hybridization demonstrated that the extended DNA fiber was an rRNA gene. Anti-fibrillarin antibody immunolabeling revealed that these rRNA genes were located in the dense fibrillar component near the fibrillar center, including at the periphery of the fibrillar center. None was in the dense fibrillar component far away from the fibrillar center. The condensed DNA clump was located in the fibrillar center. Further observations showed that the rRNA genes in the nucleolus were all arranged around the fibrillar center and associated with the DNA clumps in the fibrillar center. Results of statistical analysis showed that the distribution region of rRNA genes occupied about one-third of the total dense fibrillar component region. Ag-NOR protein showed a similar distribution pattern to that of rDNA. Immunolabeling of an anti-RNA/DNA hybrid antibody demonstrated that the transcription sites of rRNA were located at the periphery of the fibrillar center and in the dense fibrillar component near the fibrillar center, and these sites were consistent with the location and arrangement of rDNA shown in situ. These results demonstrated that transcription of rRNA takes place around the fibrillar center and at the periphery, whereas the dense fibrillar component that was far away from fibrillar center was the non-transcription region. The DNA clumps within the fibrillar center were probably the anchoring sites for rDNA arrangement.
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Affiliation(s)
- Tao Wei
- Department of Cell Biology, School of Life Sciences, Peking University, 100871, China.
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Abstract
The nucleus is the cellular organelle in which the bulk of the genomic information is stored. From studies using fluorescence microscopy with optical sections of fixed cells, a picture of an organized nuclear structure has emerged. Recently, the application of the green fluorescent protein (GFP) as a fluorescent dye allows the visualization of nuclear dynamics in live cells. Using four-dimensional fluorescence microscopy, the nuclear structures within an interphase nucleus are perceived to have dynamic domains. Structural analyses of a living plant nucleus contribute to our understanding of the genome information process in a particular cell in multicelluar systems.
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Affiliation(s)
- Naohiro Kato
- Biotechnology Center for Agriculture and the Environment, Rutgers, The State University of New Jersey, 59 Dudley Road, Foran Hall, New Brunswick, New Jersey 08901-8520, USA
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Utama B, Kennedy D, Ru K, Mattick JS. Isolation and characterization of a new nucleolar protein, Nrap, that is conserved from yeast to humans. Genes Cells 2002; 7:115-32. [PMID: 11895476 DOI: 10.1046/j.1356-9597.2001.00507.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND The nucleolus is the site of rRNA synthesis and processing in eukaryotic cells, but its composition remains poorly understood. RESULTS We have identified a novel nucleolar RNA-associated protein (Nrap) which is highly conserved from yeast (Saccharomyces cerevisiae) to human, with homologues in mouse, Drosophila melanogaster, Caenorhabditis elegans, Arabidopsis thaliana, Schizosaccharomyces pombe, and other species. In the mouse, we have found that Nrap is ubiquitously expressed and is specifically localized in the nucleolus. We have also identified splice variants in human and mouse, and defined the intron-exon structure of the human Nrap gene. Nrap is inherited into daughter nuclei by associating with the condensed chromosomes during mitosis. RNase treatment of permeabilized cells indicated that the nucleolar localization of Nrap is RNA dependent. The effects of actinomycin D, cycloheximide and 5,6-dichloro-beta-d-ribofuranosyl-benzimidazole on Nrap expression and distribution in cultured cells suggest that Nrap is associated with the pre-rRNA transcript. CONCLUSIONS Nrap is a large nucleolar protein (of more than 1000 amino acids), and is a new class of protein with new structural and functional motifs. Nrap appears to be associated with ribosome biogenesis by interacting with pre-rRNA primary transcript.
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Affiliation(s)
- Budi Utama
- Centre for Functional and Applied Genomics, Institute for Molecular Bioscience, University of Queensland, St. Lucia, QLD 4072, Australia
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Olson MOJ, Hingorani K, Szebeni A. Conventional and nonconventional roles of the nucleolus. INTERNATIONAL REVIEW OF CYTOLOGY 2002; 219:199-266. [PMID: 12211630 PMCID: PMC7133188 DOI: 10.1016/s0074-7696(02)19014-0] [Citation(s) in RCA: 144] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
As the most prominent of subnuclear structures, the nucleolus has a well-established role in ribosomal subunit assembly. Additional nucleolar functions, not related to ribosome biogenesis, have been discovered within the last decade. Built around multiple copies of the genes for preribosomal RNA (rDNA), nucleolar structure is largely dependent on the process of ribosome assembly. The nucleolus is disassembled during mitosis at which time preribosomal RNA transcription and processing are suppressed; it is reassembled at the end of mitosis in part from components preserved from the previous cell cycle. Expression of preribosomal RNA (pre-rRNA) is regulated by the silencing of individual rDNA genes via alterations in chromatin structure or by controlling RNA polymerase I initiation complex formation. Preribosomal RNA processing and posttranscriptional modifications are guided by a multitude of small nucleolar RNAs. Nearly completed ribosomal subunits are exported to the cytoplasm by an established nuclear export system with the aid of specialized adapter molecules. Some preribosomal and nucleolar components are transiently localized in Cajal bodies, presumably for modification or assembly. The nonconventional functions of nucleolus include roles in viral infections, nuclear export, sequestration of regulatory molecules, modification of small RNAs, RNP assembly, and control of aging, although some of these functions are not well established. Additional progress in defining the mechanisms of each step in ribosome biogenesis as well as clarification of the precise role of the nucleolus in nonconventional activities is expected in the next decade.
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Affiliation(s)
- Mark O J Olson
- Department of Biochemistry, University of Mississippi Medical Center, Jackson 39216, USA
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27
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Tao W, He M, Hao S. Ultrastructural localization of active genes inAllium cepa cells. CHINESE SCIENCE BULLETIN-CHINESE 2001. [DOI: 10.1007/bf02900468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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28
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Schwarzacher HG, Mosgoeller W. Ribosome biogenesis in man: current views on nucleolar structures and function. CYTOGENETICS AND CELL GENETICS 2001; 91:243-52. [PMID: 11173865 DOI: 10.1159/000056853] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Nucleoli develop when preribosomes are synthesized at the chromosomal nucleolar organizer regions. Typically they consist of at least three nucleolar subcompartments, the fibrillar center (FC), the dense fibrillar component (DF), and the granular component (GC). The understanding of the functional arrangements of these subcompartments relates to aspects in cell biology, pathology, and virus research. In the present review morphological studies are discussed in the light of molecular findings. The available data confirm the hypothesis that rDNA transcription is connected with the DF but not necessarily with the presence of an FC. Within the DF, rDNA transcription is restricted to foci, possibly representing single transcribing genes. FCs may serve to store inactive transcription factors, to initiate rDNA transcription, and may provide structural support for transcription. The GC can be interpreted as a collection of maturing preribosomes. More recently the nucleolar subcompartments were focused on in the context of virus research and tumor biology.
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29
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Abstract
An understanding of the functional organization of nucleoli, the sites of ribosome biosynthesis, is limited by the present uncertainty about the topological arrangement of the transcribing rRNA genes. Since studies with “standard” nucleoli from somatic cells produced conflicting results, we have examined the amplified nucleoli of Xenopus oocytes. These nucleoli are unique in that they contain high copy numbers of rRNA genes, are not attached to chromosomes, lack non-ribosomal DNA and can be examined in light microscopic spread preparations of nuclear contents. By immunostaining and confocal microscopy we show that in growing stage IV oocytes the sites of rDNA are surrounded by the dense fibrillar component. The rDNA is actively transcribed as revealed by BrUTP injection into oocytes and localization of components of the nucleolar transcription machinery (RNA polymerase I and the transcription factor UBF). At the ultrastructural level, the rDNA sites correlate with the fibrillar centers of amplified nucleoli fixed in situ. The results provide clear evidence that the transcriptionally active rRNA genes are confined to the fibrillar centers of the oocyte nucleoli and open the possibility to analyze the protein composition of almost native, transcriptionally highly active nucleolar chromatin by immunofluorescence microscopy.
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Affiliation(s)
- C Mais
- Department of Cell and Developmental Biology, Biocenter of the University of Würzburg, Am Hubland, 97074 Würzburg, Germany
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30
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Tao W, He J, Jiao M, He M, Hao S. Configuration of nucleolar DNAin situ in nucleolus ofAllium cepa cells. CHINESE SCIENCE BULLETIN-CHINESE 2001. [DOI: 10.1007/bf03183211] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
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31
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Barneche F, Steinmetz F, Echeverrı́a M. Fibrillarin Genes Encode Both a Conserved Nucleolar Protein and a Novel Small Nucleolar RNA Involved in Ribosomal RNA Methylation inArabidopsis thaliana. J Biol Chem 2000. [DOI: 10.1016/s0021-9258(19)61499-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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32
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Abstract
The function of the nucleolus as a factory for assembling ribosomal subunits is well established, but many unrelated activities have been discovered over the past decade. Our understanding of the dynamics of nucleolar structure and its reassembly at the end of mitosis has recently advanced and the small nucleolar RNAs have been shown to be major players in the processing and modification of preribosomal RNA. Unexpectedly, the nucleolus also seems to play a role in nuclear export, sequestering regulatory molecules, modifying small RNAs, assembling ribonucleoprotein (RNP) and controlling aging.
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Affiliation(s)
- M O Olson
- Dept of Biochemistry, The University of Mississippi Medical Center, Jackson, MS 39216-4505, USA.
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